The quality of the aluminum (substrate) used in track manufacturing varies greatly. This results in variable adhesion performances. To minimize this variability in adhesion, one can chemically treat the aluminum. Unfortunately, chemical treatment is expensive and requires special facilities. In this invention, the use of silane minimizes variability in adhesion of cleaned but untreated aluminum.
Walker, JCT, 52, 49-61 (1980), disclosed the general concept of organofunctional silanes adhesion promoters for use with organic surface coatings on metallic substrates. EP 0540 040 A1 discloses a room-temperature curable organopolysiloxane composition having highly durable adhesion to various substrates including glass, plastics and metal. U.S. Pat. Nos. 4,963,636, 5,008,349 and Japanese Publication Hei 3-408 (1991) also disclose silicone containing primers or adhesion promoters. Baker et al, IN. J. Adhesion and Adhesives, 12, 73-74 (1992) disclose the use of silane as an adhesion promoter in the manufacture of aircraft. U.S. Pat. No. 5,206,285 discloses a mixture of amino silane and epoxy silane compounds, in a particular molar ratio, as a corrosion inhibitor. Such references disclose application of silane adhesion promoters to polyurethane paints, sealing agents, adhesives and injection molding materials. U.S. Pat. No. 5,159,970 discloses the use of an aminosilane as an adhesion agent on a pattern before applying layers of ceramic material to build up a shell mold. Walker, In JOCCA (J. Oil Col. Chem. Assoc.), 1982, 65, 415 and 436-443, discloses the use of organosilanes as adhesion promoters for two-pack urethane and epoxide paints on aluminum and mild steel substrate, wherein the adhesion promoters are either applied as pretreatment primers or incorporated into the paint. Walker discloses improvement in adhesion to both degreased substrates and to grit blasted surfaces. See also Walker, JCT, 52. no. 670 (1980) and Walker, JOCCA, 1984, 4, 108-112, and Cave et al, J. Adhesion, 1991, 34, 175-187.
The latter references do not mention application to automotive surfaces. In the automotive industry, high performance finishes or coatings meeting the highest standards of durability and appearance are necessary. This involves surface treatment of the metal substrate before applying a plurality of layers of different coatings, for example, a primer, primer surfacer, basecoat and/or clearcoat. With respect to trucks, as compared to cars or airplanes, it is usually not practical to treat the metal substrate by acid anodizing with phosphates or chromates to prepare the surface prior to applying the finish. Instead, the surfaces of trucks are typically subjected to mechanical surface treatment in order to obtain satisfactory adhesion of the subsequent finish. For example, sanding of the surface is commonly practiced. Nevertheless, finishers continue to suffer adhesion losses and other problems when painting tracks in the process of manufacture. This invention solves adhesion problems with respect to the finishes on trucks without increasing process costs significantly.